Osmotic devices manufactured for delivering useful agents are known to the prior art in U.S. Pat. Nos. 3,845,770 and 3,916,899, both issued to Theeuwes and Higuchi. The devices disclosed in these patents are made with a wall formed of a material that is permeable to an exterior fluid and substantially impermeable to the passage of agent. The wall surrounds a compartment that contains an agent. The device delivers the agent through a passageway in the wall to the exterior of the device. Osmotic delivery systems embracing a different structure and mode of operation also are known to the prior art in U.S. Pat. No. 4,177,256, issued to Michaels and Guillod. The systems disclosed in this patent consists of depots of drug particles dispersed in and surrounded by a polymer. The systems releases drug by depots rupturing to deliver drug to the exterior of the system. The manufactures of these patents are remarkably effective for delivering many agents to different environments of use.
While the above inventions represent significant and pioneering advancements in the delivery art, and while they are useful for dispensing numerous agents, there is an occasional instance where the delivery of an agent may require more control than is provided by prior art for its delivery to the environment of use. For example, if the agent is very soluble in fluid imbibed into the compartment, or in a separate operation the agent is very soluble in fluid imbibed into the depots, the agent in either instance may be delivered individually at a high rate and in an amount in excess of that required for obtaining a preselected result. In the light of the above presentation, it will be appreciated by those versed in the art, that if a delivery device is made available that integrates and simultaneously uses the physical and chemical embodiments of the prior art device and system, in a single unit device for enhanced control of the delivery of agents, such a device would have a positive value and also represents an unexpected advancement in the art.